Circumferentially grooved, longitudinally striped bobbin



May 15, 1962 .1. H HILL 3,034,743

CIRCUMF'ERENTIALLY GROOVED. LONGITUDINALLY STRIPED BOBBIN Filed Feb. 25, 1960 INVENTOR JAMES HOLMES HILL BY fiM ATTORNEY United States Patent Ofilice 3,034,743 Patented May 15, 1962 3,034,743 CKRQUMFERENTIALLY GROOVED, LONGETUDI- NALLY STRTPED BOBBIN James Holmes Hill, Martinsville, Va., assignor to E. I. du Pont ale Nemours and Company, Wilmington, Deb,

a corporation of Delaware Filed Feb. 25, 1960, Ser. No. 10,941 3 Claims. (Cl. 242-11832) This invention relates to textile bobbins used to support yarn packages. More specifically, this invention relates to bobbins of this type having modified surfaces to substantially eliminate internal sloughing of the yarn wound thereon and to facilitate delivery of last winds from the bobbin and removal of yarn heels.

A familiar tapered yarn package is prepared generally in conjunction with a twisting operation by winding yarn onto a flangeless bobbin. The bobbin usually comprises a tubular metal reinforcing barrel and an outer cover or sleeve composed of plastic, paper or the like. A representative bobbin having a plastic sleeve is shown in US. Patent No. 2,659,547 to Broadbent et al. The use of such bobbins is of considerable advantage. The metal barrel provides the strength characteristics, especially important when winding retractable yarns such as nylon. The outer sleeve provides the necessary surface characteristics in a material which is readily restored or modified. Plastic sleeves are preferred since they are more durable than paper sleeves. In addition, worn or used sleeves can be readily reconditioned or replaced with sleeves of the same or different composition, thereby elfecting considerable savings.

However, despite the many advantages it has been observed from time to time that the surface characteristics of plastic covered bobbins are such that internal sloughing of the yarn windings adjacent the bobbin resulted. Internal sloughing, i.e., lateral shifting of the yarn windings is a quality control problem of considerable magnitude. Its occurrence may lead to eclipsed transfer tails, a reduction in yarn quality and, in extreme cases, poor package formation. In particular, a definite correlation has been observed between the frequency and severity of internal sloughing and the incidence of poor transfers and warping defects respectively.

The prior art suggests numerous ways to increase the surface friction characteristics of textile bobbins. These procedures generally involve grit blasting, knurling, grooving, coating, taping and/ or variety of similar operations. However, no one of these has been successful in effecting the substantial elimination of internal yarn sloughing. Moreover, by the very nature of such modifications, the operation commonly termed heel cutting, i.e., the step of removing waste yarn or the last few layers of yarn windings by cutting them from the bobbin, cannot be carried out in a conventional manner. There would result, when using conventional heel-cutting equipment, numerous nicks, cuts, gouges and the like in the bobbin surface, since the as-modified surface is more prone to such injuries, all of which greatly increase the number of yarn defects during subsequent use of the bobbin.

One object of this invention is to substantially eliminate internal sloughing of yarn wound onto bobbins having plastic surfaces. Another object of the invention is to permit facile cutting of heels of the yarn wound onto such bobbins. Other objects will become apparent on the ensuing description of the invention.

The objects of this invention are accomplished by providing a textile bobbin with a plastic core surface having formed over a major portion thereof between about 50 to about essentially circumferential grooves per inch of winding surface, i.e., per inch of bobbin length covered by yarn, each of such grooves being between about 0.001 and about 0.003 inch in depth, such a bobbin having in addition at least one longitudinal stripe of width sufficient to permit facile passage of conventional heel-cutting equipment, e.g., a knife, but not so wide as to sacrifice the advantages of the grooving. Preferably, the grooves are smoothly rounded in profile, as are the corresponding ridges thereof. The peripheral ribs separating adjacent circumferential grooves may form a series of broken rings of equal diameter, each lying in a plane substanially perpendicular to the longitudinal axis of the bobbin. Alternatively, the grooves may be disposed substantially as a discontinuous helix of low pitch angle, usually not exceeding about one degree. Preferably the longitudinal stripe portion comprises less than 25% of the circumferential surface. The stripe portion is depressed and may therefore be unmodified, i.e., contain no grooves. However, axial grooves may be present in the depressed stripe if desired, although no material advantage is obtained thereby.

The preferred embodiment of this invention is a flangeless bobbin having a Kralastic (styrene copolymer extrusion compositions supplied by the Naugatuck Chemical Company) sleeve with between about 60 to about 70 circumferential grooves per inch molded in the winding surface thereof, each groove being between about 0.0015 and about 0.0025 inch in depth, the grooves being interrupted to provide three smooth stripes, each about inch in width, the stripes being disposed parallel to the bobbin axis and spaced with angular symmetry, i.e., at intervals, around the surface of the bobbin, the surface of the stripe being radially lower than the ridges of the circumferentially threaded portion, preferably from about 0.0003 to about 0.001 inch lower. If the stripe were raised from the outer surface of the bobbin, rather than depressed, tension plucks could result when the last winds are removed from the bobbins. These become especially apparent with nylon which has an atfinity for highly polished surfaces. A bobbin suitable for modification in this manner is shown in the aforementioned patent to Broadbent et al.

In the ensuing discussion of the invention the term bobbin refers generally to the conventional package supports onto which yarn customarily is wound. Such bobbins may be flanged or flangeless and may be other than cylindrical in shape, e.g., may be conical. Yarn refers to filamentary stucture in'general, such as strands, filaments, thread, string, and the like. The term plastic, when used with reference to the surface composition of the bobbin, includes all such compositions which ordinarily lend themselves to that application; it refers particularly to both thermoplastic and thermosetting materials such as the phenolics, the polystyrenes, acetate-butyrates, etc.

The present invention is more readily understood by referring to the accompanying drawing, wherein:

FIGURE 1 is a side elevation of a bobbin representative of the present invention;

FIGURE 2 is a corresponding top view of the bobbin of FIGURE 1;

FIGURE 3 shows a portion of the surface of a bobbin having circumferential grooving;

FIGURE 4 shows a similar view of a bobbin having helical grooving in the surface thereof.

Referring to FIGURES l and 2 of the drawing, bobbin 1 is of generally cylindrical form, consisting of plastic sleeve member 2 which is fitted over barrel member 3. The plastic surface of sleeve member contains circumferential grooves 4 over the surface thereof, interrupted to form 3 longitudinal stripes 8. Stripes 8 are spaced 120 apart about the surface of sleeve member 2.

In FIGURE 3 the circumferential grooves and intervening peripheral ridges are illustrated by reference numerals 4 and 5 respectively at enlarged area A. In FIGURE 4 the helical grooves and corresponding ridges are represented by reference numerals 6 and 7 respectively at enlarged area B. It is to be understood however, that the grooved portion represented in FIGURES 3 and 4 actually extends over the entire winding surface, i.e., that portion of the bobbin covered by yarn, and is interrupted only to form the longitudinal stripes which permit heel cutting.

The bobbin of this invention may be prepared in a number of ways, each having advantages in particular applications and with particular materials. The groove may be molded, cut, or otherwise superimposed into the core surface. When the bobbin has a plastic sleeve, the sleeve may be grooved before or after its application to the barrel member. The preferred sleeve is prepared from extruded Kralastic tubing which is inflated in a suitable mold to form the surface grooves and the longitudinal stripe(s). The grooved sleeve can be applied with heat to a steel barrel. Subsequent cooling provides a tight sleeve fit on the barrel. Another method for applying this sleeve is by means of an air ram which both inflates the sleeve and urges it onto the barrel. Alternatively, the groove may be molded into the surface after the sleeve is applied. The sleeve also may be formed directly on the barrel by spraying or dipping the barrel in a suitable plastic melt or solution. In the case of solid plastic bobbins, the grooves may be added during molding or later, as the stock is cut to size.

The depth of the grooves in the bobbin surface is conveniently measured with a contour projector, so as to magnify the profile of the surface, permitting thereby ready characterization. Alternatively, the surface profile may be expressed in terms of roughness values based on conventional R.M.S. units, i.e., the average root mean square roughness in microinches. The determination of the roughness data may be accomplished in a number of ways: a direct reading Profilometer is useful. The R.M.S. roughness is determined as outlined in Machinerys Handbook, 14th edition, page 291.

The bobbins of the present invention having a groove depth between about 0.001 and about 0.003 inch exhibit 5 an average surface roughness of between about 100 and about 600 root mean square microinches. The preferred bobbins, having groove depths between about 0.0015 and about 0.0025 inch, usually exhibit a surface roughness between about 150 and about 450 root mean square microinches.

The number of grooves per inch of winding surface and the depth thereof are important. Both contribute to provide a bobbin surface of a particular and unique charac ter not achieved in a surface of equivalent roughness grooves, e.g., as might be obtained by knurling the bobbin surface. Nor is the comparable performance achieved in a bobbin having fewer but deeper grooves, as such a surface usually has adverse effect on yarn quality and, especially, transfer efficiency. Such undesirable behavior is seen, for example, in a prior art bobbin having ca. circumferential grooves per inch, each groove being about 0.007 inch in depth. By employing a greater number 80) of shallower grooves 0.001 inch), the propensity toward internal sloughing is increased, owing in part to the unmodified portion of the surface present as heel-cutting stripes and also to insuificient surface friction per se. Only with the bobbin of this invention is it believed possible to efiiect the substantial elimination of internal sloughing and maintain yarn quality at a consistently high level,

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while providing for the ready removal of yarn heels from the nearly unwound package.

Internal sloughing in a yarn package is noted from an apparent lengthening of the package and becomes progressively more evident as the unwinding operation is continued. It may occur at either end of the package or at both ends. In many of the sloughed packages, the transfer tail is partially or completely covered by shifted yarn windings. Severe sloughing leads to package erosion, usually apparent after unwinding only a fraction of the yarn from the package. The impetus for sloughing ordinarily stems from the handling of the package subsequent to its preparation. Sloughing also is a reaction to the compressive forces which develop, e.g., in a package of nylon yarn.

The bobbin of this invention is useful in most of the conventional yarn packaging operations, and particularly during pirn formation. It serves especially Well with retractable yarns such as nylon, and also with the other synthetic fibers. The plastic surface is durable, greatly resisting nicking and scratching, resulting in prolonged bobbin life. When worn, it is easily replaced and, in most instances, the cover composition may be reclaimed for further use. The core surface modification herein described ordinarily remains useful throughout the life of the core surface; in cases where core wear is severe, the modified surface can be restored to its original condition. The use of this bobbin results in the substantial elimination of internal sloughing, but does not adversely affect yarn quality.

Heel cutting with conventional equipment is accomplished without damage to the modified surface by virtue of the stripes provided thereon, which stripes surprisingly do not detract from the utility of the bobbin. The novel bobbin permits improved delivery of the last few windings of yarn from its surface, which leads to enhanced transfer efficiency and completeness of runout in magazine creeling. As last winds of yarn are pulled from the bobbin surface, yarn touches or rubs across the top of the grooved threads. The reduced bobbin surface to yarn contact area results in lower friction or resistance to removal of the yarn windings and would appear to be responsible at least in part for the unexpected advantage of improved transfer efficiency. Other advantages inherent in the practice of this invention will occur to those undertaking its practice.

What is claimed is:

1. An improved bobbin assembly for supporting and stabilizing packages of retractable textile yarns of synthetic polymeric composition without lateral shifting of the yarn windings along the bobbin axis, said bobbin assembly comprising a rigid elongated metallic hollow cylindrical member having an exterior surface, a replaceable cylindrical layer of durable wear-resistant plastic material surrounding said cylindrical member and secured to said exterior surface, said layer comprising an external cylindrical surface provided with about 60 to closely spaced continuous circumferential grooves per inch evenly distributed along the axial dimension of said layer external surface, said grooves having a radial depth from said external surface of between 0.0015 and 0.0025 inch and having smoothly rounded profiles, said grooved external surface of said layer further provided with a plurality of axially extending circumferentially spaced radially depressed blank areas interrupting said grooves, said depressed blank areas formed by cutaway portions in said external surface of said plastic layer, said cutaway portions extending radially inwardly from said surface from between 0.0003 to 0.001 inch, the intersections of said depressed blank areas with said grooved portions of said plastic layer forming radially projecting axially extending rows of abutments in the surface of said bobbin assembly, said abutments constructed and arranged to deflect and distort turns of yarn wrapped around said bobbin assembly significantly out of a circular configura- 6 tion at the intersections of said depressed blank areas said plastic material essentially comprises a styrene with said grooved portions of the plastic layer so that copolymer. circumferentially spaced points of increased pressure are created by said projecting abutments in each turn of such References fi t d in th file Of this patent yarn to assist in securing the yarn against lateral shifting 5 UNI ED STA PAT along the bobbin axis under compressive forces of the ompleted package i h 10, 2. The improved bobbin assembly of claim 1 in which 2,163,618 Muller Jun? 27, 1939 said metallic member is formed of a steel composition. 2,273,373 Perry 1942 3. The improved bobbin assembly of claim 2 in which 10 

